1. Field of the Invention
The present invention relates to an arrangement for coupling a harness between an electronic control unit located outside an engine and a fuel injector located inside the engine.
2. Description of the Related Art
A common rail-type fuel injection system for a diesel engine is generally equipped with an electronic control unit (ECU) for determining an amount and timing of fuel injection such that fuel injection matches an engine running condition. Specifically, ECU outputs an electric signal to an electromagnetic valve provided in a fuel injector such that the injector is activated to inject a desired amount of fuel to the engine at a desired timing.
ECU is coupled with the fuel injector by harness. This harness is referred to as injector harness in this specification. In general, ECU is mounted inside a passenger compartment or an engine room, which is outside the engine. The injector is attached to a cylinder head, and its connection to the harness is often located inside the engine (e.g., inside a head cover). In such an arrangement, the injector harness must penetrate the head cover.
Referring to FIG. 8 of the accompanying drawings, illustrated is one of known ways of passing the injector harness through the head cover. Specifically, a packing "c" provided between a cylinder head "a" and head cover "b" has through holes "d", which extend in the lateral direction, such that two injector harnesses (not shown) enter the cylinder head cover therethrough. This engine has four cylinders, and each of the two injector harnesses is used for each two of the four cylinders.
Referring next to FIG. 9 of the accompanying drawings, illustrated is another conventional way for passage of the injector harness (Japanese Patent Application Laid-Open Publication No. 3-260335). A terminal (connector) member "e" is embedded in a side wall of the head cover such that its front (or outer) face is exposed to the outside of the head cover and its back (or inner) face is exposed to the interior of the head cover. FIG. 9 illustrates the outer face. Wires are connected between the fuel injector and terminal "e" inside the head cover, and the harness extending from ECU is plugged into the terminal "e" outside the engine. The terminal "e" is fixed to the head cover side wall by bolts. Reference symbol "f" designates a flange having two bolt holes and "H" designates height of the flange.
However, the approach of FIG. 8 must employ a packing "c" of complicated shape. This would deteriorate air tightness and oil tightness at the packing "c". In particular, vibration from the cylinder head "a" is directly transmitted to the interface between the cylinder head "a" and head cover "b" so that high quality of sealing is required to the packing "c". Such requirements may not be met if the packing "c" has a complicated contour. Strong vibration is also transferred to the injector harness from the cylinder head "a" so that the injector harness may be damaged or disconnected.
The arrangement of FIG. 9 also has a shortcoming. Because the flange "f" has the bolt holes, its height "H" inherently becomes relatively large. As a result, the head cover also has large height. A tall head cover is not desirable if the engine should be designed to be compact.